INV.13 RED CABBAGE INDICATOR

Name: Jason Graham
Year 9 Science
INV.13 RED CABBAGE INDICATOR
Experimental Team
Jason Graham, Redge Weule, Kiara Shepherd
Aim
To extract the coloured substance from red cabbage, and use it to test acids and bases.
Materials
• 2 or 3 large leaves from a fresh red cabbage
• sharp knife and chopping board
• two 250 mL beakers
• hotplate (or burner, tripod and gauze)
• stirring rod
• 6 test tubes and test tube rack
• dilute hydrochloric acid (0.5 M)
• dilute sodium hydroxide solution (0.5 M)
•
Method
1 Put cut Red Cabbage in a beaker.
2 Add water to just cover the cabbage pieces.
3 Boil the cabbage mixture for 5–10 minutes. The water should turn a dark colour, and the leaves should
almost lose their colour.
4 Let the mixture cool. Then carefully decant the coloured solution into another beaker. Alternatively, you
could strain the mixture through a sieve.
5 Add a small amount of dilute hydrochloric acid to a test tube and label it. Add some sodium hydroxide
solution to another test tube. Now add a few drops of red cabbage extract to each tube.
6 In the same way, use the red cabbage extract to test the various household substances you have
collected. For each substance, record any colour change.
Results
Substance
Observations
Before
Solution was clear
After
Solution turned red.
Sodium Hydroxide
(BASE)
Solution was clear
Solution turned yellow
Water
Solution was clear
Solution turned purple
Cream of Tartar
Solution was white
Solution turned pink.
Antacid
Solution was clear/pale yellow
Solution turned pale green.
Vitamin C
Solution was orange
Solution turned pale red.
Hydrochloric Acid
(ACID)
[INV.13 RED CABBAGE INDICATOR]
Name: Jason Graham
Year 9 Science
Hydrochloric Acid
Water
Sodium Hydroxide
Discussion
The extract solution created by boiling the cabbage leaves was purple in colour. When it was added to
water (neutral solution) the water remained a purple colour. The extract turned red in an acid-solution
(hydrochloric acid) and green-yellow in a basic solution (sodium hydroxide).
1. What colour is your red cabbage extract in a neutral solution (water)?
Purple.
What colour is it in acidic solutions?
Red.
In basic solutions?
Green / Yellow.
2. Which household substances are the most acidic?
Vitamin C
Which are the most basic?
Antacid
How do you know?
It was similar in colour to the base tested.
3. Suggest why the red cabbage extract is called an acid–base indicator.
Easy to differentiate between Acids and bases.
[INV.13 RED CABBAGE INDICATOR]
Year 9 Science
Name: Jason Graham
Conclusion
The experiment was successful in extracting acid-base indicator from Red Cabbage and using it to test
household substances for pH.
[INV.13 RED CABBAGE INDICATOR]
Name: Jason Graham
Year 9 Science
Appendix
Substance
Observations
Before
Solution was clear
After
Solution turned Red/pink
Sodium Hydroxide
(BASE)
Solution was clear
Solution turned yellow
Water
Solution was clear
Solution turned purple/blue
Tartaric Acid
When dissolved in water was white
Solution turned pale red/pink
Glaxo Eno
(Antacid)
White Vinegar
Pale yellow
Pale blue
Solution was clear
Solution turned Red/pink
Lemon Juice
Clear/cloudy
Solution turned pale red/pink
Windex
Blue
Green
Sodium
BiCarbonate
Conditioner
White
Pale blue/green
Pale green
purple
Shampoo
Pale red
purple
Milk
While
Solution purple/pale red
Hydrochloric Acid
(ACID)
[INV.13 RED CABBAGE INDICATOR]

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